Robot arm joint, particularly for haptic and/or cobotic uses

Abstract

A motorized robot arm joint comprising a first segment ( 1 ), a second segment ( 2 ) moveably mounted on the first segment and driven by an actuator ( 8 ) connected to a control unit ( 20 ) and rigidly connected to a mounting ( 5 ) that has a first friction element ( 10 ) and is mounted on the first segment such that it moves when subjected to a driving force greater than a predetermined threshold and presses the first friction element against a second friction element ( 12 ) that is rigidly connected to the second segment. One of the friction elements is wedge-shaped and has a bisecting plane that is substantially parallel to a plane of movement of the second segment such that it can be engaged between two jaws ( 13.1, 13.2 ) of the other of the friction elements, the jaws having surfaces arranged so as to make point-by-point contact with the wedge shape.

1 . A motorized robot arm joint comprising a first segment ( 1 ), a second segment ( 2 ) moveably mounted on the first segment and driven by an actuator ( 8 ) connected to a control unit ( 20 ) and rigidly connected to a mounting ( 5 ) that has a first friction element ( 10 ) and is mounted on the first segment such that it moves when subjected to a driving force greater than a predetermined threshold and presses the first friction element against a second friction element ( 12 ) that is rigidly connected to the second segment, characterized in that one of the friction elements is wedge-shaped and has a bisecting plane that is substantially parallel to a plane of movement of the second segment such that it can be engaged between two jaws ( 13 . 1 ,  13 . 2 ) of the other of the friction elements, the jaws having surfaces arranged so as to make point-by-point contact with the wedge shape. 
     
     
         2 . The joint as claimed in  claim 1 , characterized in that the surfaces of the jaws ( 13 . 1 ,  13 . 2 ) are spherical. 
     
     
         3 . The joint as claimed in  claim 1 , characterized in that the jaws ( 13 . 1 ,  13 . 2 ) are assembled with a clearance in a direction substantially normal to the bisecting plane. 
     
     
         4 . The joint as claimed in  claim 1 , characterized in that the actuator includes a motor ( 8 ) with an output shaft linked to a first wheel that is engaged with a drive element of the second segment. 
     
     
         5 . The joint as claimed in  claim 4 , characterized in that the second segment ( 2 ) is assembled on the first segment ( 1 ) to pivot about an axis ( 3 ) perpendicular to the first segment and is rigidly connected to a second wheel ( 9 ) that is coaxial to the axis of rotation such that the second wheel forms the drive element of the second segment. 
     
     
         6 . The joint as claimed in  claim 5 , characterized in that the mounting ( 5 ) is designed to pivot, and the mounting and the motor ( 8 ) are substantially coaxial. 
     
     
         7 . The joint as claimed in  claim 1 , characterized in that the predetermined threshold is set by calibrating at least one spring ( 15 ) arranged to exert a force on the mounting ( 5 ) that opposes a movement of same to bring the friction element into contact. 
     
     
         8 . The joint as claimed in  claim 7 , characterized in that the mounting ( 5 ) has a seat with a substantially V-shaped bottom ( 17 ) designed to receive a pin ( 16 ) arranged to slide in a plane of movement of the mounting, the spring ( 15 ) extending between the segment and the pin to press the latter against the bottom of the seat. 
     
     
         9 . The joint as claimed in  claim 7 , characterized in that the spring ( 15 ) extends tangentially to a trajectory of the mounting to oppose a movement of the mounting to bring the friction elements into contact.